Kono, Junichiro2022-09-232022-09-232022-052022-04-20May 2022Komatsu, Natsumi. "Thermoelectric and Electronic Transport Studies of Ultrahigh-Conductivity Carbon Nanotube Fibers." (2022) Diss., Rice University. <a href="https://hdl.handle.net/1911/113332">https://hdl.handle.net/1911/113332</a>.https://hdl.handle.net/1911/113332Carbon nanotubes (CNTs) are marvelous one-dimensional (1D) materials with extraordinary electronic, mechanical, thermal, magnetic, and optical properties. However, the 1D properties of individual CNTs are often lost in randomly ordered macroscopic assemblies. Recently, macroscopic fibers of aligned carbon nanotubes (CNTs) with ultrahigh conductivity (> 10 MS/m) have emerged. Understanding of transport processes in these ordered CNT assemblies is critical for further conductivity improvement, but systematic experimental investigations have not been performed to date. Here, we have studied thermoelectric and electrical properties of CNT fibers produced by the solution spinning method. We first measured thermoelectric quantities while tuning the Fermi energy and obtained a giant thermoelectric power factor. In probing the temperature and magnetic field dependence of the electrical conductivity of the fibers, we observed a metallic behavior in a wide temperature range (40-300 K) – i.e., the conductivity monotonically increased with decreasing temperature. At low temperatures (< 50 K), strongly temperature-dependent negative magnetoresistance appeared, which is a hallmark of the phenomenon of weak localization, suggesting that the electron transport at low temperatures is quantum coherent. In addition to macroscopic CNT fibers with diameters of ~10 μm, we also performed conductivity measurements on individual crystalline CNT bundles (with diameters ~ 20 nm and lengths ~ 10 μm) that constitute the fibers, to determine the dimensionality and coherence lengths of carriers.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Carbon nanotubeselectronic transportthermoelectric properties nanomaterialsThesis2022-09-23